Calvert Cliffs Nuclear Power Plant Unit 2 was manually shut down Tuesday morning due to a failure of equipment associated with the unit’s steam generator feed pump.

At 5:45 a.m. Tuesday, the reactor was prompted to shut down by the trip of a steam generator feedwater pump due to high vibrations that appear to be caused by a failed mechanical coupling between the pump’s motor and the pump, according to an email from U.S. Nuclear Regulatory Commission spokesman Neil Sheehan.

CCNPP spokesman Kory Raftery said Thursday morning that unit 2 was “safely synchronized” to the grid at about 8:50 a.m. Thursday.

As of 3:30 p.m. Tuesday, Raftery said all “initial indications” point to the failure of equipment associated with the unit’s stean generator feed pump and the coupling between the pump’s motor and the pump.

“At no time was the public’s safety at risk,” Raftery said, adding that the plant’s system responded as designed without complications.

In Sheehan’s email, he said the two resident inspectors “will continue to review the event and the response by plant personnel to [the shutdown].”

Raftery explained the plant will continue to investigate the shutdown, make the necessary repairs to the unit and test the unit befire resynching to the electric grid.

“We have no information to suggest this shutdown is related to the automatic shutdown [on May 8],” Raftery said Tuesday morning.

The May 8 shutdown was due to an electrical fault involving turbine electro-hydraulic controls circuitry that resulted in an increase in reactor vessel pressure.

Sheehan said in the email that if a plant has more than three shutdowns during the previous 7,000 hours of operations, the NRC’s level of insight will increase.

During a phone interview Tuesday afternoon, Sheehan said CCNPP Unit 2 has two more to go before that insight is increased. He said having “two in a short span of each other means they’re going to want to be very mindful.”

Raftery said the current investigation is the plant’s focus right now to ensure that the unit can “run reliably for the long haul.”